Polymeric prosthetic liners (or “liners”) have become the interface of choice among amputees due to various beneficial characteristics thereof. These characteristics include, for example, comfort, security of suspension, protection of the residual limb, and ease of use. Modern liner technology allows amputees to employ a liner as the sole (stand-alone) interface between their residual limb (which is also commonly referred to as a residuum or amputation stump) and the interior of a prosthetic socket—in contrast to known wool or knit socks and cushioned socks or sheaths that must be worn in multiple layers and/or various combinations to provide sufficient cushioning and protection to a residual limb.
Prosthetic liners may be non-suspensory in nature. Non-suspensory liners are commonly referred to as “cushion liners.” Prosthetic liners may optionally be suspensory in nature and may, therefore, include a docking element that facilitates suspension by mechanical attachment of the liner to the socket of a prosthesis. Suspensory liners are commonly referred to as “locking liners” or “cushion locking liner.” Liners can be of standard “off-the-shelf” design, meaning the liner is of generic shape and will fit a range of residual limb shapes and sizes. Alternatively, liners may be custom designed for a particular amputee.
Liners may be comprised of various polymeric materials, including silicone, urethane, and thermoplastic elastomers (TPE) gels. Liners are now commonly made using various block copolymer and mineral oil gel compositions. Such polymeric materials, particularly block copolymer and mineral oil gel compositions, have proven themselves to provide an optimal level of comfort for most users.
It is also known to construct such liners with an outer layer of fabric. For example, the present assignee produces patented fabric-covered liners having an interior of exposed polymeric gel for contacting and cushioning an amputee's residual limb, and an integrated outer layer of fabric for, among other things, increasing the wear resistance of the liner, and facilitating donning/doffing and insertion of the liner-covered residual limb into a prosthetic socket.
As would be understood by one of skill in the art, liners as described above are frequently used by lower limb amputees. Lower limb amputees generally fall into one of two categories: above knee (AK) amputees and below knee (BK) amputees. In the case of a BK amputee, the knee joint is still present and, thus, a bending of the residual limb at the knee joint will still occur during ambulation. While the prosthetic hard socket of a BK prosthesis is generally recessed to accommodate the knee joint, BK amputees typically wear a liner that extends over the knee joint to some point along the thigh of the residual limb. Consequently, bending of the knee joint occurs under cover of the liner.
In a typical below-knee (BK) prosthesis an amputee's stump tends to “piston” in the socket: during ambulation the stump will come up in the socket of the prosthesis until the attaching means holding the prosthesis to the wearer causes the prosthesis to lift with the stump. On the way down, air may be trapped between the residuum and stump sock, or between the prosthesis socket and sock, or between a socket liner and a sock.
With wool and cotton socks which tend to breathe and which are not airtight, this pistoning effect is not a major problem with regard to the generation of sound effects. Since wool and cotton tend not to tightly form fit a residuum, the amputee typically packs a material around the residuum once it is placed into the prosthetic device or adds additional socks to increase thickness or puts on thicker socks in order to provide necessary fit. However, for socks which do not breathe and which are made from, e.g., polymeric material, a problem occurs when the residuum pistons in the prosthetic device: sound effects such as sucking and gurgling noises are generated which are obtrusive and inappropriate, often embarrassing the wearer. In addition, such air pockets produce non-uniform pressures and loading discontinuities on the skin, irritating it.
Finally, many amputees experience a swelling of the stump. When the residuum is in a prosthetic socket the stump tends to contract significantly, and when taken out of the socket the stump tends to expand within minutes of removal. This expansion and contraction of the residuum contributes to the development of air pockets and the generation of obtrusive noises since a sock which may have provided a comfortable fit on the expanded stump becomes a loose fit with air pocket opportunities when the residuum is placed inside the prosthetic socket. In addition, and over time, an amputee's residuum tends to adjust in size, usually shrinking. As these changes occur they increase the tendency for the pistoning effect, described above, to occur. In addition to the embarrassment caused by the sound effects generated by pistoning, cushioned socks which allow or promote air pocket formation quickly wear out and, if not replaced often, lead to lesions, etc. on the residuum.
Known cushioned residuum sheaths and socks are frequently purely tubular in shape, but may also be conical in shape. In either case, these devices often do not provide a form fit on an amputee's residuum. Further, regardless of whether such sheaths/socks are provided with internal and/or external cushioning material they frequently fail to avoid air pockets. While a stump may generally have a roughly conical or cubical shape there are invariably recessed areas on, e.g., the medial side of the prominent tibia bone. Generally, on the left side of a below knee residual limb, the recessed area will be predominantly on the right side of the tibia bone. There is also typically a smaller recessed area on the left side. For right side residual limbs the predominant recessed area is on the left side of the bone, with smaller recessed areas on the right side. Usually the greatest recess occurs immediately below the patella, on either side. In addition, left side amputees typically have a right side bias to the bony prominence of the below knee stump, and right side amputees have a similar bias to the left side. Conventional tubular or conical elastic socks simply cannot account for these several variable conditions without using extremely high levels of elastic tension which compress the outer-most points along the stump's circumference, causing discomfort and a non-uniform fit.
Amputees typically attach a prosthetic limb to their residual limb by means of a rigid socket, liner, and a suspension means. The rigid socket is often custom fabricated to match the shape of the intended users residual limb and may be made of thermoplastic or fiber-reinforced thermoset materials, but can also be made from wood, metal, etc. Since such hard materials are generally uncomfortable when in intimate contact with the skin over long periods of time, especially under load bearing conditions, liners and/or prosthetic socks are often used as interface members between the hard socket and the residual limb to increase comfort. Early liners were commonly made of an open cell foam, such as Pelite or Kemblo, but were also made of silicone, urethane, etc., type of materials. See, for example, U.S. Pat. No. 5,258,037 and U.S. Pat. No. 5,376,132, both incorporated herein by reference. Prosthetic socks, as mentioned above, may be made of wool, cotton, synthetic materials, etc., and amputees tend to prefer liners and socks which are easily changed to facilitate cleaning, to accommodate volume changes in the residual limb, or to accommodate different user activities.
Suspension systems which help to hold a prosthetic limb in place may or may not be an integral part of the rigid socket and/or liner. Examples of suspension systems include supracondylar or waist belt, joint and corset systems, neoprene or latex sleeves, socket ears which grip the condyles, suction or pin and lock systems such as those where the pin is attached to a liner and the lock is attached to a hard socket, etc. Examples of various suspension systems may be found in U.S. Pat. No. 4,923,474, U.S. Pat. No. 4,923,475, U.S. Pat. No. 5,007,937, U.S. Pat. No. 5,108,456, U.S. Pat. No. 5,201,773, U.S. Pat. No. 5,201,774, U.S. Pat. No. 5,246,464, U.S. Pat. No. 5,263,923, U.S. Pat. No. 5,314,497, U.S. Pat. No. 5,387,245, U.S. Pat. No. 5,376,131 and U.S. Pat. No. 5,405,405, all incorporated herein by reference.
As block copolymer based prosthetic liners have become increasingly popular, it can be understood that further development of prosthetic liners using such materials would be desirable. The present invention is directed to such a further development.